1. Field of the Invention
The present invention relates to a laser processing apparatus.
2. Description of the Related Art
In a laser processing apparatus equipped with a processing nozzle that projects laser beam on a workpiece, it is known to make provisions so that the processing nozzle and the workpiece are moved relative to each other by performing a gap control in order to maintain a constant spacing (hereinafter referred to as a “gap”) between the tip of the processing nozzle and the surface of the workpiece during execution of laser processing such as cutting on the workpiece. If, for example, a power failure such as a power outage or voltage drop occurs when performing laser processing under gap control, there is a danger that the processing nozzle may accidentally hit the workpiece due to such causes as a malfunction of a gap sensor or a delay in the activation of a safety brake.
Various laser processing apparatus capable of preventing the processing nozzle from accidentally hitting the workpiece have been proposed in the prior art. For example, Japanese Examined Utility Model Publication No. H03-44388 (JP H03-044388 Y) discloses a laser processing apparatus equipped with a processing head dropping prevention mechanism which, upon cutoff of power to a driving device for moving the processing head up and down, actuates a spring-biased engaging member to stop the rotation of a ball screw being driven by the driving device.
On the other hand, Japanese Patent No. 2751766 (JP 2751766 B) discloses a laser processing apparatus equipped with a mechanism for positioning the processing head and preventing it from slipping down by causing a stopper provided on a movable part to which the processing head is attached and a stopper provided on a fixed part having a processing head guide to abut against each other. One or the other of the stoppers provided on the movable part and the fixed part is adapted to be able to change the position at which it abuts against the other stopper.